Change in the Isotopic Composition of Transmutation 135Cs Targets during Radiochemical Recycling

¹³⁵Cs transmutation in the presence of other cesium isotopes is studied. The change in the concentration of the ancillary starting nuclides and the activity of the targets when they are recycled are analyzed. It is shown that decreasing the initial ¹³⁷Cs content in a target to 1% is an adequate level of isotopic separation of cesium. It is established that the ¹³³Cs and ¹³⁴Cs concentration is quasistationary, the increase in target activity is negligible and is determined by the accumulation of ¹³⁷Cs, and for a long time there is no need to separate the cesium isotopes from irradiated targets.     

t—BAMBP萃取色谱法分离铷,铯的研究

对ｔ Ｂ Ａ Ｍ Ｂ Ｐ萃取色谱法分离铷、铯进行了研究。采用萃取色谱柱实现了铷、铯的完全分离。建立了简便、高效的铷、铯放化分离流程,对铯的去污系数大于 １０６,铷的回收率大于 ８０％ 。     

Fusion-Driven Transmutation of Fission Product Cesium in its Elemental Form

Assuming fission reaction as a dominant energy source for a long-term perspective, the goal of transmutation of fission products is to cut their increasing accumulation and to keep their inventories at easily manageable level. Opposite to relatively short-lived ¹³⁷Cs (T_1/2=30yr) whose natural decay converge equilibrium mass to the level of order of 11 per GW of fission energy, an approach to similar equilibrium inventory for long- lived ¹³⁵Cs (T_1/2=2.3×10⁶ yr) requires artificial transmutation that preassumes its isotopic separation in the most studies. The present paper addresses cesium transmutation without preliminary isotope separation that means an approach to equilibrium for all the isotopes including stable ¹³³Cs. A high-flux blanket driven by Fusion Neutron Source with ITER-like parameters is proposed to transmute cesium in the elemental form. Transmutation efficiency is estimated in terms of equilibrium inventory and characteristic time to reach equilibrium both governed by the mean life-time of nuclides in transmuter. The analytical results show that the mean life-time of the target isotope ¹³⁵ Cs is as short as 21 yr which is in more than order of magnitude shorter than achieved in advanced fission reactors. It reveals that one Fusion Neutron Source with ITER-like parameters could transmute elemental cesium from 23 PWRs, the fraction of power associated with transmutation being as small as 3%.     

Molecular laser isotope separation versus atomic vapor laser isotope separation

In this work, the competitive molecular and atomic laser isotope separation methods are investigated to evaluate the potential of each une for more economical fuel fabrication of enriched uranium celas which can be practically used in light water reactors (LWR). The advantages, drawbacks and feasibility of various techniques of laser isotope separation including AVLIS and the main MLIS methods such as MOLIS, CRISLA, and SILARC techniques have been reviewed. Laser isotope separation (LIS) deserves an intensive research, because laser techniques have a number of advantages over traditional ones, such as highly selective elementary separation event, possibility of separating the required isotope, low energy consumption, short start up time and practically single-stage production, which may economize fuel processing [11.     

Studies of laser induced cesium and rubidium hydride formation in vapor cells and their application for isotope separation

We present the results of studies of alkali hydride formation in vapor cells under laser irradiation. Two mechanisms are studied: formation in the cell volume in the presence of hydrogen and formation on the laser irradiated cell window. The first mechanism is investigated in a room-temperature cesium vapor cell, while the second one in a heated natural rubidium cell. The studies are aimed at isotope separation by means of selective laser excitation of the vapor with subsequent hydride formation. In the first case we obtained the intensity dependence of the absorption and fluorescence and could evaluate, by comparing with calculations, the rate constant of the two-step reaction of CsH formation. In the second case a solid layer deposition was observed on the cell window and interpreted as rubidium hydride.     

玉米对Cs+的富集能力及Cs+对其抗氧化指标影响的研究

研究了玉米对不同浓度Cs⁺的富集差异,并探讨Cs⁺对玉米幼苗抗氧化指标的影响。结果表明：玉米幼苗中Cs⁺含量均与处理浓度和时间呈显著正相关,根是主要的富集器官,其次为茎;在20mmol/L处理28d后,根的Cs⁺含量分别是茎和叶的1.6和5.1倍;根、茎、叶Cs⁺含量分别是0.5mmol/L处理浓度的16.3、18.0和24.7倍。所有处理时期根、茎、叶转运系数和富集系数与处理时间呈显著正相关,均为茎的转运系数大于叶的转运系数,富集系数由高到低依次为根、茎、叶。对抗氧化生理指标的分析发现,随Cs⁺浓度的增加和处理时间的延长,玉米幼苗POD和CAT活性均表现为先应激性上升后下降的动态变化,丙二醛和过氧化氢含量均呈上升趋势,且与处理时间均呈显著正相关,这表明POD和CAT清除有害过氧化物的能力有限,高浓度时均受到一定程度的抑制,抗氧化体系在一定程度上被破坏。     

Sorption and Desorption Behavior of 60Co, 85Sr,and 137Cs in a Porous Tuff

Sorption experiments of ⁶⁰Co, ⁸⁵Sr and ¹³⁷Cs were carried out to study sorption characteristics onto a porous tuff. Sorption kinetics and rate controlling step were examined. The effects of particle size on sorption and distribution ratio were also investigated. Desorption experiments were carried out by using extracting reagents to distinguish sorption mechanisms such as reversible sorption in groundwater condition, ion exchange, association with ferro-manganese oxides or oxyhydroxides, and irreversible fixation. Strontium sorbed onto the tuff surface mainly by the ion exchange reaction which was fast and reversible. Cobalt and cesium do not sorb by simple step. The main sorptive binding of cobalt was the association with ferro-manganese oxides and the secondary one was the irreversible fixation. Diffusion into the lattice of rock minerals controlled the sorption rate of cobalt. The main sorption of cesium was the irreversible fixation, secondary one was the ion exchange.     

A high power MOPA free—electron laser with narrow line—width

A new kind of MOPA configuration to obtain a high power free-electron laser with very narrow line-width that can satisfy the requirements of some applications such as the laser isotope separation has been proposed.which is investigated by onedimension simulations.     

Validation of 134Cs, 137Cs and 154Eu single ratios as burnup monitors for ultra-high burnup UO2 fuel

A measurement station has been built for the non-destructive investigation of burnt fuel rod segments through high-resolution gamma spectrometry. Four UO₂ pressurised water reactor fuel rod segments with different burnup levels between 50 and >100 GWd/t and ⩽10 year cooling time have been experimentally characterised using gamma-ray spectrometry to determine ¹³⁴Cs, ¹³⁷Cs and ¹⁵⁴Eu and their corresponding concentration ratios. Experimental errors of ∼2% (1σ) for the ¹³⁴Cs/¹³⁷Cs ratio were obtained for most of the segments. In parallel, pin cell depletion calculations have been performed for each segment using the deterministic code CASMO-4. Measured and calculated ratios have then been compared with the purpose of deriving and validating pin-averaged single-ratio burnup indicators for very high burnups. It is shown that the ¹³⁴Cs/¹³⁷Cs ratio, frequently used as a burnup monitor, is considerably less precise for values exceeding 50 GWd/t; discrepancies of ∼16% are found between measured and calculated values, increasing with burnup up to ∼23%. The ratios built with the ¹⁵⁴Eu concentration show even much larger discrepancies, essentially because this isotope is rather poorly predicted as revealed by just using different basic cross section data.     

Potential application of a nanocomposite:HCNFe@polymer for effective removal of Cs (I) from nuclear waste

This study highlights new opportunities for the preparation of Cobalt Hexacyanoferrate(CoHCNF)@poly aniline nanocomposite as an adsorbent to efficiently remove Cs (I) ions from water. A chemical co-precipitation method was utilized to prepare CoHCNFe@poly aniline nanocomposite nanostructure. The TEM and SEM images of the product showed that it consists of semi-spherical particles with sizes ranging from 50 to 500 nm. Experimental parameters affecting Cs (I) sorption such as pH, adsorbent dosage, contact time, initial concentration of metal ion and temperature were studied. The maximum adsorption capacity (q) for cesium ions obtained from the Langmuir model at room temperature and 60 °C were 92.12 and 181.81 mg g⁻¹ respectively. It is clear that this adsorbent has effective removal properties for adsorption of Cs(I) from radioactive waste compared with other adsorbents.The kinetic data were analyzed by the pseudo-first-order and the pseudo-second-order kinetic models; consequently, the pseudo-second-order model was the best to describe the adsorption of Cs (I) ions. The equilibrium data were fitted to the three isotherm models: Freundlich, Langmuir and Dubinin–Radushkevich (D–R), and as a result the Langmuir model produced the best fit for the experimental data. Thermodynamic parameters showed that the adsorption of Cs (I) ions onto the nanocomposite was endothermic and spontaneous. The mechanism of Cs (I) ions sorption was discussed.     

同位素铯源小尺度参考辐射蒙特卡罗模拟研究

为研究同位素铯源小尺度参考辐射的计量特性与散射特征,采用蒙特卡罗程序MCNP开展了模拟研究,并将模拟结果与实验结果进行对比。本文厘清了边长为600mm的铅屏蔽立方体同位素铯源小尺度参考辐射的计量特性与空间散射射线的特征信息,明确了待检仪器探头尺寸对小尺度参考辐射中散射成分的影响规律,确定了用于表征散射特征的计量特征点的位置。     

Determination of impurity radionuclides in <Superscript>131</Superscript>Cs solutions

The radiochemical purity of a ¹³¹Cs solution used in brachytherapy is studied. After separating ¹³¹Cs from the neutron irradiated targets BaO, Ba(NO₃)₂, and BaCO₃, the contribution of impurities was evaluated: 0.015% for ¹²⁴Sb and 0.012% for ¹³²Cs. The contribution of the parent ¹³¹Ba to cesium solutions was, on average, 0.0067% for BaO, 0.01% for Ba(NO₃)₂, and 0.011% for BaCO₃.     

Development of Conventional Quadrupole Mass Analyzer for RI Target Analysis and Its Performance

A Knudsen-cell-based quadrupole mass analyzer has been developed for the analysis of a small amount of RI sample. To achieve a high signal/noise ratio, a continuous dynode electron multiplier was installed at the end of the mass filter and was operated in a pulse counting mode. Furthermore, the cylindrical shape molecular trap was set around the mass analyzer to reach high degree of vacuum and to reduce the RI contamination area in the apparatus.

The isotope ratio of ¹³⁵Cs/¹³⁷Cs samples has been measured to demonstrate the performance of the mass analyzer. Taking the advantage of the Knudsen-cell's precise controllability over temperature, the contribution of the isobar ¹³⁷Ba was successfully removed in the mass spectrum of cesium. With samples containing about 0.3μg ¹³⁷Cs and almost the same amount of ¹³⁵Cs, the isotope ratio measurement with the total error of 3% has been achieved. The molecular trap was also shown to be effective to reduce the contamination area in the apparatus.     

用无机离子交换法从酸性高放废液中去除铯研究进展

60年代以来人们十分关注用离子交换法从配性高放废液中去除和回收∧137Cs。本文对比和评价了沸石、多价金属磷酸盐、磷钼酸铵及其复合离子交换材料、不溶性亚铁氰化物、钛硅化合物等无机离子交换剂。结合笔者的最新研究成果，并考虑了含铯废液交换剂的进一步处置问题，提出了为我国生产堆高放废液中去除∧137Cs的无机离子交换材料，对我国的后处理中去除铯的研究提供参考。     

Burnup Determination of High Burnup and Dry Processed Fuels Based on Isotope Dilution Mass Spectrometric Measurements

Destructive methods were used for the burnup determination of a PWR nuclear fuel irradiated to a high burnup in power reactors, and of a dry processed fuel fabricated from a spent PWR fuel and irradiated in the Hanaro research reactor. The total burnup was determined from a measurement of the Nd and Cs isotope burnup monitors. The methods included U, Pu, ¹⁴⁸Nd, ¹⁴⁵Nd+¹⁴⁶Nd, total of the Nd isotopes, ¹³³Cs and ¹³⁷Cs determinations by the isotope dilution mass spectrometric method (IDMS) by using quadrupole spikes (²³³U, ²⁴²Pu, ¹⁵⁰Nd, and ¹³³Cs). The methods involved two sequential anion exchange resin (AG 1X8 and 1X4) separation procedures and a Cs purification with a cation exchange resin (AG 50WX4) separation procedure. The results obtained by the Nd and Cs isotopes from the mass spectrometric measurement were compared with those by the ORIGEN code.     

Commissioning of a high-resolution collinear laser spectroscopy apparatus with a laser ablation ion source

Collinear laser spectroscopy is a powerful tool for studying the nuclear spins,electromagnetic moments,and charge radii of exotic nuclei.To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion-beam Facility （BRIF） and the future High Intensity Heavy-ion Accelerator Facility （HIAF）,we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system.The overall performance of this state-of-the-art technique was eva...     

裂变放射性核素^90Sr、^137Cs分离的研究进展

对近年来裂片核素^90Sr、^137Cs的分离技术如沉淀法、萃取法、无机离子交换法等研究的进展进行评述，同时展望了可能潜在的高放废物（液）处理技术路线。对汽液矿化处理^90Sr、^137Cs废液做了简单介绍。新型高效萃取剂冠醚（DtBuCH18C6）和杯冠芳烃（BOBCalixC6）对^90Sr和^137Cs离子有比较好的选择性；绿色萃取技术如离子液体萃取技术、超临界流体萃取技术也在^90Sr、^137Cs萃取分离中得到应用。晶态钛硅酸盐（CST）和金属硫化物（KMS-1）在碱性条件下对^137Cs和^90Sr有比较高的选择性。汽液矿化处理能将含有^90Sr、^137Cs的低放废液转化成稳定的硅铝酸矿物。虽然理论上能有效地将^90Sr和^137Cs从高放废液中分离出来，但是高放乏燃料的最终处置技术还有待进一步探索。     

Indirect assessment of 135Cs activity in the ventilation system of the Ignalina NPP RBMK-1500 reactor

The accumulation of long-lived ¹³⁵Cs isotope in the ventilation system components of the Ignalina NPP Unit 2 was investigated by spectrometric measurements and mathematical modeling. Volumetric activities of fission noble gas and other short-lived isotopes (⁴¹Ar, ^85mKr, ⁸⁷Kr, ⁸⁸Kr, ⁸⁸Rb, ¹³³Xe, ^133mXe, ¹³⁵Xe, ¹³⁸Xe, ¹³⁸Cs) have been measured by gamma spectrometric technique. Modeling of radionuclide transport in the ventilation system provides possibility of determining essential transport parameters: effective gas flow, mean gas retention time, deposition rate of aerosols. Estimated parameters were used for indirect evaluation of difficult to measure ¹³⁵Cs isotope activity in the ventilation system components: a delay chamber and aerosol filters. The results show that the major part of ¹³⁵Cs activity is accumulated in aerosol filters, whereas the total surface activity of the delay chamber is considerably lower. Specific activities of the ventilation system components of the Ignalina NPP Unit 2 are below the clearance levels for ¹³⁵Cs.     

复合无机离子交换材料及其在水体放射性Cs检测中的应用

离子交换法速度快、能与检测仪器联用，已逐渐成为水体中放射性Cs的主要富集方法。由于单一的离子交换材料无法兼顾抗辐照性、强选择性和高吸附速率等性能，因此研发兼顾各种性能的新型离子交换材料将成为提高水体中放射性Cs富集效率的关键。本文通过总结复合无机离子交换材料在水体放射性Cs富集分离方面的研究进展及相关应用，分析了各类复合无机离子交换材料的优缺点，并针对不同复合无机离子交换材料的制备提出了溶胶 凝胶、多孔支撑体和有机物黏接等改进方法。这为制备更高效的复合无机离子交换材料和提高放射性Cs检测的效率提供了参考，也为离子交换法在其他领域中的应用提供了新的思路。     

Isotope separation methods for self-consistent nuclear energy system

It is known that for transmutation of fission products(FPs) in the concept of self-consistent nuclear energy system(SCNES) based on fast neutron reactor it is necessary to apply isotope separation of some FPs to keep neutron balance (to decrease parasitic capture of neutrons by stable isotopes). It is a question whether such FPs isotope separation can be feasible or not within amount of nuclear fission energy production. So it is necessary to consider isotopic content of FPs after fast reactor and to choose energetically appropriate isotope separation method for each radioactive FPs taking into account safe radioactivity level of FPs. In this paper we discuss about isotope separation method for SCNES. Isotopic composition of FPs was calculated using tables of fission yields from ²³⁹Pu fission. It isshown that concentrations of radioactive isotope in the main FPs to be isotopically separated are significant and vary from 2% in ruthenium up to 74% in iodine. We consider new isotope separation methods developed recently such as plasma separation process (PSP) based on selective ion cyclotron resonance heating and atomic vapor laser isotope separation (AVLIS) as a possible candidates. It seems to be energetically profitable to combine various methods to achieve desired separation characteristics. Since the most of FPs have a high initial concentration of radioactive isotope, PSP method seems to be a good candidate for first stages of separation process. We consider the main parts of energy expenditure in one PSP module and its separation characteristics. Estimations of energy consumption in multistage isotope separation process of FPs give maximum value 100keV/fiss. using PSP only and 3MeV/fiss. using AVLIS only. We can significantly decrease these values using AVLIS after PSP when concentration of target isotope in separation cascade will become sufficiently low. We can affirm that energy consumption in isotope separation of FPs is less than 60 MeV of electricity per one fission in nuclear reactor.